The present invention relates to a method of and an apparatus for producing methanol.
Methods and apparatuses for the conversion of methane into methanol are known. It is known to carry out a vapor-phase conversion of methane into a synthesis gas (mixture of CO and H2) with its subsequent catalytic conversion into methanol as disclosed, for example, in Karavaev M. M., Leonov B. E., et al “Technology of Synthetic Methanol”, Moscow, “Chemistry” 1984, pages 72-125. However, in order to realize this process it is necessary to provide complicated equipment, to satisfy high requirements for the purity of the gas, to spend high quantities of energy for obtaining the synthesis gas and for its purification, and to have a significant number of intermittent stages from the process. Also, for medium and small enterprises with the capacity of less than 2,000 tons/day it is not economically feasible.
Russian Patent No. 2,162,460 includes a source of hydrocarbon-containing gas, a compressor and a heater for compression and heating of the gas, and a source of oxygen-containing gas with a compressor. It further includes successively arranged reactors with alternating mixing and reaction zones and a means to supply the hydrocarbon-containing gas into a first mixing zone of the reactor and the oxygen-containing gas into each mixing zone, a recuperative heat exchanger for cooling of the reaction mixture through a wall by a stream of cold hydrocarbon-containing gas of the heated hydrocarbon-containing gas into a heater, a cooler-condenser, a partial condenser for separation of waste gasses and liquid products with a subsequent separation of methanol, a pipeline for supply of the waste gas into the initial hydrocarbon-containing gas, and a pipeline for supply of waste oxygen-containing products into the first mixing zone of the reactor.
In this apparatus, however, it is not possible to provide a fast withdrawal of heat of the highly exothermic oxidation reaction of the hydrocarbon-containing gas because of the inherent limitations of the heat exchanger. This leads to the necessity to reduce the quantity of supplied hydrocarbon-containing gas and, further, it reduces the degree of conversion of the hydrocarbon-containing gas. Moreover, even with the use of oxygen as an oxidizer, it is not possible to provide an efficient recirculation of the hydrocarbon-containing gas due to the rapid increase of the concentration of carbon oxides. A significant part of the supplied oxygen is wasted for oxidation of CO into CO2, which additionally reduces the degree of conversion of the initial hydrocarbon-containing gas to useful products and provides a further overheating of the reaction mixture. The apparatus also requires burning an additional quantity of the initial hydrocarbon-containing gas in order to provide the utility needs of a rectification of liquid products. Since it is necessary to cool the gas-liquid mixture after each reactor for separation of liquid products and subsequent heating before a next reactor, the apparatus is substantially complicated and the number of units is increased.
A further method and apparatus for producing methanol is disclosed in the patent document RU 2,200,731, in which compressed heated hydrocarbon-containing gas and compressed oxygen-containing gas are introduced into mixing zones of successively arranged reactors, and the reaction is performed with a controlled heat pick-up by cooling of the reaction mixture with water condensate so that steam is obtained, and a degree of cooling of the reaction mixture is regulated by parameters of escaping steam, which is used in liquid product rectification stage.
Other patent documents such as U.S. Pat. Nos. 2,196,188; 2,722,553; 4,152,407; 4,243,613; 4,530,826; 5,177,279; 5,959,168 and International Publication WO 96/06901 disclose further solutions for transformation of hydrocarbons. It is believed that the existing methods and apparatus for producing methanol can be further improved.